How to set current position to previous postion

In your game script, have a variable that keeps the position of the car. In Update() decide if the car is still under control or not. If it is under control, then update the variable. If the car is skidding or crashing then don't update the variable. If the car has finally crashed and come to a halt, then change the position of the car to the last one you stored. In pseudo-code:

 Update() {
   if car is under control
     last_position = position;
 
   if car is skidding or crashing
     play some kind of warning sound
 
   if car has crashed
     let player know to drive more slowly
     position = last_position
 }

Note - this is not Javascript or c# - it is meant to illustrate the logic you will need to implement.